1. Technical Field
The present invention relates to a filter chip element and a method of preparing the same.
2. Description of the Related Art
Recently, data transmitting and receiving functions of an electronic device such as a digital television (TV), a smart phone, and a notebook computer at a high frequency band have been widely used. Also, in the future, it is expected that multifunctional and compound electronic devices formed by connecting electronic devices to each other via a universal serial bus (USB) or other communication ports as well as a single electronic device are highly used.
In order to quickly transmit and receive data, data may be transmitted and received through as many as possible internal signal lines at a high frequency band of GHz moved from a previous frequency band of MHz.
When data is transmitted and received between a main device and a peripheral device at a high frequency band of GHz in order to transmit and receive a large amount of data, it is difficult to smoothly process the data due to signal delay and other interferences.
In particular, various port to port connections such as a communication line and an image and audio signal lines are used as in a digital TV, issues in terms of internal signal line delay and transmitting and receiving distortion may occur more frequently.
In order to overcome this problem, counter electromagnetic interference (EMI) components are disposed around connections between IT products and peripheral devices. Conventional wound and stack type counter EMI components have large sizes of chip elements and low electrical properties, and thus, may be used only in a limited region of a large size circuit board. However, due to the use of slimmed, miniaturized, compound, and multifunctional electronic devices, there is a need for counter EMI components satisfying these functions.
In order to form a conventional counter EMI component, ferrite powders and solvents, which have the same composite, a binder, other dispersants, or the like are mixed in a slurry form or a paste form, die casting or print process is performed on the resultant mixture to prepare green sheets, and then the green sheets are stacked to a desired thickness and are fired.
If necessary, during the firing, the green sheets are pressed with a predetermined weight. A fired substrate may have different thicknesses at an edge portion and a central portion, may be bent, and may break or crack due to weak shock Thus, it is not appropriate to use the fired substrate as a ferrite substrate for EMI and electromagnetic compatibility (EMC), such as a common mode filter product.
Firing density of the fired substrate locally varies. Air voids are formed in a non-fired portion. Thus, chemical solutions used in photolithography penetrate into the fired substrate, thereby causing internal air voids or erosion.
A ferrite substrate used in a thin film type common mode filter is formed by forming internal conductive patterns on a fired base substrate by photolithography process and then mixing ferrite and resin to form a ferrite composite layer thereon. However, the ferrite composite layer has lower magnetic permeability and a lower Q value than the fired ferrite substrate formed on a lower portion, thereby causing impedance reduction of actual chip characteristic.
The ferrite composite layer requires dispersibility of ferrite powders and resin, adhesion therebetween, and the like.
Conventional ferrite resin has low dispersibility, difficulty in control of powder particle sizes, and low adhesion between interfaces, and thus, a resin layer formed of the ferrite resin may crack and have low deformation strength, thereby causing dimension error. Thus, due to the dimension error, magnetic permeability and a Q value which are important characteristics of an inductor chip element are reduced.
It is difficult to form an internal circuit required to obtain various functions with a small area in order to satisfy miniaturization of internal conductive patterns, and thus, there is a limit in using conventional wound and stack type noise filters in an electronic component. Accordingly, there is a need to manufacture a thin film type common mode filter in order to address the problems of wound and stack type common mode filters.
As shown in FIG. 1, the thin film type common mode filter is manufactured by forming an insulating layer 20 including an organic material on a fired ferrite substrate 10, forming conductive patterns 30 thereon and then mixing organic resin and ferrite powders to form a ferrite composite layer 40.